Color temperature of a light source is a temperature of an ideal black body when the ideal black body radiates at a certain temperature a light with the same color as that of a light emitted by the light source. The bluer the light color is, the higher the color temperature is; and the redder the light color is, the lower the color temperature is. The color temperature below 3300K gives people a sedate atmosphere and a feeling of warmth; the intermediate color temperature between 3000K and 5000K gives people a feeling of refreshment; and the color temperature above 5000K gives people a feeling of cold. Different application scenarios may require light sources with different color temperatures.
The conventional technical solution is to use a constant-voltage module together with multiple constant-current Direct-Current to Direct-Current (DC/DC) power supply circuits to adjust current of each load branch. As shown in FIG. 1, the DC/DC constant-current circuit may be a high frequency conversion circuit. Output of the constant-voltage module is used as input of the multiple constant-current circuits. Each DC/DC constant-current circuit performs constant-current control independently, and the value of output current of each load branch can be set independently as required, so as to adjust brightness of light-emitting diodes (LEDs) with different colors or different color temperatures, and thereby achieves adjustment for color or color temperature of a light source.
In the above solution, since each circuit for adjusting current of a LED needs one separate constant-current DC/DC circuit, the cost is high.